Coatings for exterior applications require good weather resistance. When an aqueous acrylate polymer emulsion obtained by emulsion polymerization is dried at room temperature or elevated temperature conditions, a coating is obtained that has acceptable durability. Because dried acrylate polymers have good durability, aqueous acrylate polymer emulsions are widely used as a resin for aqueous paints. However, when a coating obtained from an acrylate polymer emulsion or from a paint comprising an acrylate polymer emulsion having a pigment incorporated therein is exposed to outdoor conditions or ultraviolet light, not only is the luster of the coating likely to be rapidly deteriorated, but the coatings also have poor gloss retention and poor water resistance.
Silicones have been used to improve weather resistance of organic resin compositions. For an example, modification of alkyd and acrylic resins with silicones improve their durability in solvent-borne coatings for exterior applications. Concerns about volatile organic compound (VOC) emissions have prompted the development of waterborne analogues. However, it is often difficult to introduce silicone materials into waterborne organic resin compositions because the silicones are incompatible and/or immiscible with waterborne organic resin compositions. Typically, very small amounts of silicones are used as additives. Consequently, silicone materials used as additives are normally not crosslinked gels or elastomeric compounds. Rather, the silicone materials used as additives are silicone oils and silicone resins. Silicone oils and resins typically are not compatible with waterborne organic resins when large amounts are added. To incorporate silicone materials into waterborne organic resins, functional silicone intermediate materials have been used to first chemically modify organic resins and then to emulsify these modified organic resins. The use of silicone oils and resins requires multiple processing steps including resin synthesis and emulsification, which are not easy to practice and adds costs to the final modified organic resin emulsion.
Therefore there is still a need for an additive which improves the hydrophobicity (water resistance), scratch resistance and gloss retention of waterborne organic resin, especially after exposure to environmental aging conditions.